Theta oscillations coordinate navigation and movement

October 13, 2015
Theta waves in the hippocampus of mice. On the left spontaneous occurrence, on the right theta waves regulated by light, which makes them more uniform and more stable. Credit: Nature Communications/FMP

Using light pulses, Berlin scientists have recently managed to control theta oscillations in mouse brain. They discovered that these brain waves coordinate movement - enabling signaling between distant brain regions – a common code for controlling mental states and behavior.

Theta oscillations were discovered in Berlin-Buch almost 80 years ago, but despite decades of intensive research, the function of this rhythm remained elusive due to the lack of tools to experimentally control and manipulate it. Theta waves occur in several regions, including the , a part of the brain where so-called "place cells" code the specific location of animals or humans during navigation. But up until recently, it was not known how or whether theta oscillations could control behavior during exploration.

A team of researchers led by Tatiana Korotkova and Alexey Ponomarenko at the FMP Institute/NeuroCure Cluster of Excellence in Berlin used optogenetics to control theta oscillations in mice. They targeted light-sensitive molecules at neuronal connections from the main pacemaker of the theta rhythm to the hippocampus, and excited these pathways using an optic fiber. "It was fascinating to see that such a major part of brain network activity – the – simply followed the pace of the light which we shone into the brain" - recall Ph.D. students Franziska Bender and Maria Gorbati.

Optogenetic control 'fine-tuned' theta oscillations, rendering them more regular, and isolating them from other influences such as sensory inputs. Therefore, this method opened the way to answering long-standing questions about the impact of theta rhythmic activity on behavior. Here the first surprise awaited researchers: as the rhythm in hippocampus was optogenetically regularized, mice changed the way they moved through environment. The animals moved slower and with a more constant speed depending on the experimentally adjusted regularity of theta oscillations.

"Brain rhythms work like traffic lights, which signal when certain neural cells should fire and when they should stay silent", summarized Alexey Ponomarenko. "More regular oscillations act as green traffic lights repeated with regular intervals. With orderly , activity of many 'vehicles' – populations of cells in hippocampus - appears to be more consistent over time".

The second surprise was that not only cortex, but also other, evolutionally much older, brain regions responded to the "traffic lights" in hippocampus, and participated in adjustment of animals' behavior. Hippocampal theta waves are transferred via the lateral septum to hypothalamus – an important brain control center which integrates vital signals including hunger and arousal. "For many years, role of hippocampal oscillations in spatial coding and memory was studied to understand how we remember our everyday experiences" – says Tatiana Korotkova. "Now we know that the 'cognitive' picture of environment constructed by hippocampus is also read out by which are able to directly regulate exploratory activity."

The brain is composed of many interlocking networks with immensely different organization, including different neural 'languages', which still need to work together to ensure an organism's survival. "We already knew that brain networks communicate via synchronization, but our 'dictionary' for decoding this activity though has never been tested in a conversation. Using optogenetics, it's now possible to participate in this communication, to learn exact meaning of signaling or words in the synchronization vocabulary, and to expand our dictionary" - explains Alexey Ponomarenko. The researchers are convinced that real-time optogenetic manipulation of neural network can further help to uncover causal role of brain dynamics in behavior, and also promote mechanistic understanding of mental disorders.

Explore further: Fluctuations in size of brain waves contribute to information processing

More information: Franziska Bender et al. "Theta oscillations regulate the speed of locomotion via a hippocampus to lateral septum pathway," Nature Communications (2015). DOI: 10.1038/NCOMMS9521

Related Stories

Fluctuations in size of brain waves contribute to information processing

February 8, 2013
Cyclical variations in the size of brain wave rhythms may participate in the encoding of information by the brain, according to a new study led by Colin Molter of the Neuroinformatics Japan Center, RIKEN Brain Science Institute.

Neural states affect learning

May 7, 2014
Theta-band activity in hippocampus after an event seems to be crucial for learning. A study at the University of Jyväskylä also proved that the absence of theta facilitated learning a simple task while training during theta ...

It don't mean a thing if the brain ain't got that swing

July 27, 2015
Like Duke Ellington's 1931 jazz standard, the human brain improvises while its rhythm section keeps up a steady beat. But when it comes to taking on intellectually challenging tasks, groups of neurons tune in to one another ...

Researchers probe link between theta rhythm, ability of animals to track location

April 28, 2011
In a paper to be published today in the journal Science, a team of Boston University researchers under the direction of Michael Hasselmo, professor of psychology and director of Boston University's Computational Neurophysiology ...

Eye movements reveal rhythm of memory formation

July 31, 2013
(Medical Xpress)—Quick eye movements, called saccades, that enable us to scan a visual scene appear to act as a metronome for pushing information about that scene into memory.

Brain waves encode information as time signals

December 16, 2013
How information is processed and encoded in the brain is a central question in neuroscience, as it is essential for high cognitive function such as learning and memory. Theta-gamma oscillations are "brain waves" observed ...

Recommended for you

Scientists discover powerful potential pain reliever

August 16, 2017
A team of scientists led by chemists Stephen Martin and James Sahn at The University of Texas at Austin have discovered what they say is a powerful pain reliever that acts on a previously unknown pain pathway. The synthetic ...

Scientists use magnetic fields to remotely stimulate brain—and control body movements

August 16, 2017
Scientists have used magnetism to activate tiny groups of cells in the brain, inducing bodily movements that include running, rotating and losing control of the extremities—an achievement that could lead to advances in ...

Researchers discover fundamental pathology behind ALS

August 16, 2017
A team led by scientists at St. Jude Children's Research Hospital and Mayo Clinic has identified a basic biological mechanism that kills neurons in amyotrophic lateral sclerosis (ALS) and in a related genetic disorder, frontotemporal ...

Scientists give star treatment to lesser-known cells crucial for brain development

August 16, 2017
After decades of relative neglect, star-shaped brain cells called astrocytes are finally getting their due. To gather insight into a critical aspect of brain development, a team of scientists examined the maturation of astrocytes ...

The nerve-guiding 'labels' that may one day help re-establish broken nervous connections

August 16, 2017
Scientists have identified a large group of biological 'labels' that guide nerves to ensure they make the correct connections and control different parts of the body. Although their research was conducted with fruit flies, ...

Navigation and spatial memory—new brain region identified to be involved

August 16, 2017
Navigation in mammals including humans and rodents depends on specialized neural networks that encode the animal's location and trajectory in the environment, serving essentially as a GPS, findings that led to the 2014 Nobel ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.